The present invention pertains to large arrays of imaging devices. A preferred implementation of the invention is applied to very long linear arrays of either photosensors or image creating structures. Such long linear arrays can be used to record or create large format documents such as posters or engineering drawings.
Image sensors for scanning document images typically have a row or linear array of photosensors together with suitable supporting circuitry integrated onto a silicon chip. Analogous devices for creating images in response to digital image data, such as LED print bars in Xerographic printers, or ink jet printheads, include a linear array of image creating structures similarly integrated onto a semiconductor silicon chip. In either case, because of the difficulty in economically designing and fabricating an array comparable in length to the width of an image to be created or recorded, various additional structures are typically used. In the scanning context, an optical reduction structure may be used to optically reduce the original image so that light from the image is reduced to the array of a single chip. In creating an image, a single chip can be reciprocated across the document. For example, in ink jet printing, a carriage may reciprocate a single chip for numerous swaths across an image substrate to create the image. However, certain advantages can be achieved if an array can be structured to record or create a very large image directly, using a full-width array.
In the scanning context, a full-width scanning device is described in U.S. Pat. No. 5,272,113. In the device described in that reference, several individual silicon chips, each with a small linear array of imaging structures thereon, are placed on a substrate in an end-to-end relationship to form what is effectively a single page width array of photosensors. A challenge of creating such a single full-width array is spacing the chips relative to one another so that the photosensors of the array are evenly spaced with a minimum of anomalies, particularly between the last photosensor of one chip and the first photosensor of the adjacent chip. Complicating the spacing challenge is that the coefficient of thermal expansion of the chips themselves may differ from the coefficient of thermal expansion of the printed wiring board or other structure upon which the chips are mounted.
The apparatus of the present invention is an imaging apparatus that includes first and second substrates, a first imaging device mounted on the first substrate, and a second imaging device mounted on the second substrate. A glass tie bar has a first portion attached to the first substrate, and a second portion attached to the second substrate. In particular implementations, the first and second portions of the tie bar are attached to the first and second substrates by an adhesive cured by a mechanism other than heat, such as by a light curable adhesive.
The method of the present invention is a method of forming an imaging apparatus. The method includes forming a first imaging subarray that includes a first printed wiring board, and a plurality of first semiconductor imaging chips, including a first end chip. The first printed wiring board has a joining end, and a portion of the first end chip projects beyond the joining end of the first printed wiring board. The method further includes forming a second imaging subarray that includes a second printed wiring board, and a plurality of second semiconductor imaging chips, including a second end chip. The second printed wiring board has a joining end, and a portion of the second end chip projects beyond the joining end of the second printed wiring board. The method further includes bringing the first imaging subarray into proximity with the second imaging subarray so that the first end chip is immediately adjacent the second end chip. A light curable adhesive is applied to the first board and to the second board. A glass tie bar is placed so that a first portion of the tie bar contacts the light curable adhesive on the first board, and a second portion of the tie bar contacts the light curable adhesive on the second board. Light is directed onto the light curable adhesive to cure the light curable adhesive.